The two hypotheses to be tested in this proposal are: (1) that surface integral membrane proteins, other than gp63, are functionally important for survival of both the promastigote and amastigote of the protozoan human parasite Leishmania major; (2) that the CD4+ T cell immune response to some of these integral membrane proteins is an important component in the development of immunity in mice to L.major. Our long term objectives are to biochemically study surface integral membrane proteins of promastigotes and amastigotes of L.major and to clone and express the genes for these proteins. Cloned genes will be derived by biochemical approaches (screening of expression libraries with defined antisera to proteins) as well as by direct screening of libraries using CD4+ T cells from immune mice. In order to establish which recombinant proteins are relevant to immunity in vivo, the T cell response to these cloned proteins will be tested in T cell assays using CD4+ T cells from resistant, susceptible and vaccinated mice. T cell clones responding to recombinant antigens will then be tested by adoptive transfer in mice to assess the role of these antigens in immunity. Once recombinant antigens are identified which elicit a response by host- protective CD4+ T cells, they will be tested in vaccine trials in mice both individually, in combination with LPG and as a live vaccine expressed in vaccinia virus. These studies will contribute new knowledge on both the biochemistry of surface membrane proteins of L.major as well as the nature of the T cell response to these proteins. These results will have direct relevance to the rational design of cocktail vaccines against Leishmania for eventual human use comprising soluble and membrane proteins and glycolipid antigens.